diff options
Diffstat (limited to 'docs/topics')
| -rw-r--r-- | docs/topics/db/models.txt | 34 |
1 files changed, 29 insertions, 5 deletions
diff --git a/docs/topics/db/models.txt b/docs/topics/db/models.txt index 2850294581..1dc1b17202 100644 --- a/docs/topics/db/models.txt +++ b/docs/topics/db/models.txt @@ -1376,11 +1376,35 @@ Field name "hiding" is not permitted ------------------------------------- In normal Python class inheritance, it is permissible for a child class to -override any attribute from the parent class. In Django, this is not permitted -for attributes that are :class:`~django.db.models.Field` instances (at -least, not at the moment). If a base class has a field called ``author``, you -cannot create another model field called ``author`` in any class that inherits -from that base class. +override any attribute from the parent class. In Django, this isn't usually +permitted for model fields. If a non-abstract model base class has a field +called ``author``, you can't create another model field or define +an attribute called ``author`` in any class that inherits from that base class. + +This restriction doesn't apply to model fields inherited from an abstract +model. Such fields may be overridden with another field or value, or be removed +by setting ``field_name = None``. + +.. versionchanged:: 1.10 + + The ability to override abstract fields was added. + +.. warning:: + + Model managers are inherited from abstract base classes. Overriding an + inherited field which is referenced by an inherited + :class:`~django.db.models.Manager` may cause subtle bugs. See :ref:`custom + managers and model inheritance <custom-managers-and-inheritance>`. + +.. note:: + + Some fields define extra attributes on the model, e.g. a + :class:`~django.db.models.ForeignKey` defines an extra attribute with + ``_id`` appended to the field name, as well as ``related_name`` and + ``related_query_name`` on the foreign model. + + These extra attributes cannot be overridden unless the field that defines + it is changed or removed so that it no longer defines the extra attribute. Overriding fields in a parent model leads to difficulties in areas such as initializing new instances (specifying which field is being initialized in |